Crash Course Astronomy: Dark Matter

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Dec 7, 2015

After a two week hiatus (we had our usual modulo(10) outtakes reel, then a week off for Thanksgiving), Crash Course Astronomy is back on the air! This week, I take a look at dark matter. Well, not a “look” per se, since you can’t really see it. But it’s there! Here’s how we know.

Writing this one was interesting. I was always taught that Fritz Zwicky discovered dark matter, but that’s not really the case. As I point out in the video, his observations showed the masses of clusters were too large, but the numbers he got were far too high, and we now know they must have been in error (or, to be more fair, his uncertainties were too large). In the end, Vera Rubin was the first to find convincing evidence that dark matter exists.

There’s an important point to make here. Rubin’s observations were made in the 1970s, and over the years they have been pretty much confirmed; we know dark matter exists. 

Fast forward. In the late 1990s, two teams of astronomers announced the existence of dark energy, which appears to be accelerating the expansion of the Universe.* In 2011, the Nobel Prize was awarded to the astronomers on those teams for the discovery.

Note the timing. We’ve known about dark matter for longer, the evidence is better, we even have an idea of what it might be and how to look for it, and several experiments are doing just that. Yet Rubin hasn’t received the Nobel for her work.

The Nobel committee that decides to whom the prize goes is capricious, to say the least. But it’s worth noting that 17 times as many men have received one as women. That ratio is slowly improving, but it’s a long, long way to parity.  

Mind you, I do think the discovery of dark energy is worthy of a Nobel, but over Rubin’s discovery of dark matter over 20 years earlier? It’s hard not to wonder just why the committee overlooks her work year after year, or the work of many other women who assuredly deserve one. While I wouldn’t go as far as call shenanigans on the committee, there are definitely biases at play here.

It’s easy to dismiss the importance of winning or not winning any given prize, but I think in many senses prizes are important. Certainly the money is nice, and it helps; many Nobel winners use their money to fund further research. But more importantly, I think, it puts a spotlight on certain research, raising awareness about the significance of a scientific discovery.

Dark matter outmasses normal matter by more than a factor of five, and its discovery forced us to rethink how we saw the Universe and our place in it. That’s pretty significant. It’s long past time the Nobel committee recognized that.

Want more? Every aired episode of Crash Course Astronomy is on our YouTube playlist!

* I won’t go into detail here; you can find out more about dark energy in this great video, and I’ll be covering it in detail in a future CCA episode. Also, full disclosure: The men who won are colleagues of mine, two of whom I worked with when I got my Ph.D.